This invention relates generally to a method and system for use in optical fiber technology. More particularly, this invention relates to a method and system for providing a high power optical adapter.
In fiber optical transmission systems, high power optical signals are being broadly employed to increase their transmission capacity over a greater distance. However, those of ordinary skill in the art now encounter technical problems and limitations as the optical signals are transmitted through the fiber optic system with higher power. FIGS. 1A and 1B illustrate a specific example of such technical problem in a fiber optical transmission system where optical connectors are commonly employed to provide low loss coupling of optical fibers. A standard single-mode optical fiber 15 is commonly connected to a standard optical connector 20. Each connector 20 has a ferrule 25 to surround and support the optical fiber 15 and to extend from the front end of the connector 20 to form a mating optical-fiber extension 30. A mating sleeve 40 has two mating inlet 35 to receive the optical-fiber extension 30 such that two segments of optical fiber can now closely engage to each other with accurately end-surface-to-end-surface alignment for optical signal transmission. Referring to FIG. 1B where two end surfaces 45 of two optical fibers 15 are mated with the mating sleeve 40 to engage to each other at an interface surface 50.
When the optical connectors are connected and disconnected in the process of carrying out the system tests, the end surfaces 45 of the fiber of the optical connectors are often contaminated from dirt, debris, grease and other contaminants. Damages often occur to the connectors 20 with the contaminants now deposited on the end-surfaces 45 of the optical connectors. Under the conditions of signal transmission of optical signals with higher power, the optically non-transmissive contaminants absorb the optical energy and become heated up by the optical signals. The heated contaminants continuously scorch, pit and finally damage the fiber end surfaces of the optical connectors. At the end, the optical connectors 20 lose the optical transmission function thus generates a problem for the entire optical signal transmission system. Due to the facts that the contaminants are very small particles and the end surfaces 45 of the connectors have very small surface areas, the problems caused by the contaminated end-surfaces in the connectors cannot be easily resolved by applying cleaning processes.
Specifically, the most popular optical connectors employed in fiber optical signal transmission systems are connectors for connecting standard single mode fibers having a mode filed diameter (MFD) of about 10 um at 1550 nm wavelength. Due to the small MFD, a very high power density is presented in transmitting the optical signals because the smaller the cross sectional area the higher the power density. Furthermore, due to the small MFD and high power density, the problems of heat generation as a result of contaminant deposit on the end surfaces 45 of the fiber connectors 20 are becoming more serious. With increased power of the signals transmitted in the optical fiber signal transmission system, the thermal damage problems becomes even more serious and an urgent demand now exists to resolve this difficulties as soon as possible.
Many efforts have been devoted to address this problem in attempt to reduce the damaging effects arising from deposit of the contaminants on the end surfaces. One approach is to reduce the power density of the optical signals at the end surfaces of the connector fiber. At these end surfaces, an operation is often carried out to connect or disconnect for system testing and other types of system reconfigurations. Most likely, the contaminants are deposited on the end surfaces. By increasing the surface area of the end surfaces will reduce the thermal damage problems as the power density is decreased with the increase of the surface area. Reduction in power density will also proportionally reduce the energy absorption and results in a lower level of heat generation. Hence, by enlarging the MFD of the optical fiber would therefore lead to a reduced power density and consequently lower level of heat generation due to optical energy absorption.
In the U.S. Pat. No. 5,594,825, special optical connectors are disclosed as that shown in FIGS. 2A and 2B. In the patented optical connectors, Kawasake et al. employ the thermal expand core (TEC) fibers which have special configuration near the end of the fiber where the surface areas are enlarged as that shown FIG. 3B. In order to reduce the unwanted effects of the connectors associated with high power density, the optical connector ferrule 25xe2x80x2 is specially shaped to adopt the TEC fibers. By replacing the standard single mode fibers with the TEC fibers 15xe2x80x2, the end surface areas 45xe2x80x2 are significantly enlarged because the MFD of the TEC fibers 15xe2x80x2 are typically 2-3 times larger than that of the standard single mode fibers, The area of the end surfaces 45xe2x80x2 is enlarged four to nine times. The power density of the optical signals is proportionally reduced to a lower level at the end surfaces 45xe2x80x2 of the TEC fibers 15xe2x80x2 than that at the end surfaces 45 of the standard single mode fibers 15. The thermal problems caused by contaminant heating thus become less serious at the end surfaces 45xe2x80x2 of the TEC fibers 15xe2x80x2 than that at the end surfaces 45 of the standard single mode fibers 15. Thus, the risks of connector damage caused by overheating at the fiber end surfaces 45xe2x80x2 of the optical connectors are substantially reduced.
Even though the special optical connectors 20xe2x80x2 utilizing TEC fibers 15xe2x80x2 can function properly and the damages caused by overheating in the connectors due to contaminant deposit are reduced, practical application of these types of connectors generates additional difficulties and inconveniences. For the purpose of employing the special TEC optical connectors 20xe2x80x2 on the existing fiber optic signal transmission systems, the installed standard optical connectors 20 has to be cut off from the single mode fibers 15 of the fiber optical transmission systems. Then, the special optical connectors 20xe2x80x2 must be spliced into the single mode fibers 15 of the fiber optical transmission systems. Due to the facts that the special optical connectors 20xe2x80x2 are not compatible with the standard optical connectors 20, this kind of fiber cutting and splicing need to be repeated many times during the system test and thus is very time-consuming. These additional cutting and splicing processes may also lead to further reliability or signal transmission problems if these cutting and splicing processes are not performed according to certain system specification. Practical difficulties thus arise from significant increase in production cost by implementing TEC fiber connector 20xe2x80x2 for providing a high-power fiber optical signal transmission systems.
Therefore, a need still exists in the art of design and manufacturing fiber-optic signal-transmission system to provide new configuration and method of manufacture the signal transmission system to overcome the difficulties discussed above. Specifically, high power optical adapters that are readily compatible with the existing fiber optical connector that can be provided at a relatively economical production cost at large quantity would be most desirable. It is also necessary to provide more flexibility and convenience of assembling and disassembling for system tests and reconfiguration such that these tasks can be more easily performed.
It is therefore an object of the present invention to provide a new and low-cost configuration for interconnecting optical fibers suitable for high power transmission without the inconveniences of repetitive fiber cutting and splicing operations. By providing a low cost, readily available and flexible high power optical adapter, the aforementioned difficulties and limitations in the prior art can now be resolved.
Specifically, it is an object of the present invention to provide a new configuration of interconnecting optical fiber by employing a novel high power optical adapter. The high power optical adapter is purposefully arranged to be compatibly adaptable with standard connectors and mating sleeve commonly employed in the optical fiber industries such that no changes of design or reconfiguration of current optical components are required. Meanwhile, the new high power optical adapter implements the TEC fiber to reduce the power density to circumvent the overheating problems. Flexibility and convenience in operations for connection, disconnection or reconfiguration to carry out different kinds of tests and repairs can now be easily performed without cutting or splicing fibers. Time and cost savings are achieved and reliability and productivity are improved by implementing this novel high power optical adapter.
It is another object of this invention to teach a new configuration of interconnecting optical fiber by employing a novel high power optical adapter which can be conveniently manufactured by employing the housing of a commonly available attenuator. Compatibility of the high power fiber optical adapter is readily achieved at low cost without extra design and manufacture efforts. The high power optical adapter can be manufactured by simply replacing the attenuator core with a TEC fiber. Cost effective implementation of this flexible high power optical adapter can therefore be realized with minimum system and component changes.
Briefly, in a preferred embodiment, the present invention discloses a low-cost high power optical adapter employed to reduce the effects of the contaminants in the high power fiber optical transmission systems. The high power optical adapter uses the exactly same housing of the standard plug style single mode optical attenuators. The attenuating fiber is replaced by a TEC fiber. The TEC fiber has an MFD of more than 25 um at one end and an MFD of about 10 um at the other end that is the same as a standard single mode fiber. In the high power optical adapter, the large MFD end of the TEC fiber is fixed at the male side of the ferrule and the small MFD end of the TEC fiber is fixed at the female side of the ferrule. When the high power optical adapter is employed, the original pair of the standard optical connectors is first disconnected from the standard mating sleeve. Then each of these connectors is mounted into the female sides of a pair of the high power optical adapters. Then the male sides of the pair of the high power optical adapters are connected together through the standard mating sleeve. During the system test, if the high power optical adapters are not needed, then the standard optical connectors can be just dismounted from the high power optical adapters and then reconnected together through the standard mating sleeve.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which is illustrated in the various drawing figures.